The present invention relates to a solubilized form of benzoyl peroxide and a method of manufacturing the solubilized benzoyl peroxide base solution. The invention also relates to a cosmetic solution which utilizes the solubilized benzoyl peroxide base as well as a method of manufacturing the cosmetic solution.
For almost 70 years, Benzoyl peroxide has been used as a keralolytic and antibacterial agent in the topical treatment of various skin conditions such as seborrhea and acne vulgaris. Basically, benzoyl peroxide dries the upper or outer layers of skin and causes that dried skin to sluff off. Benzoyl peroxide has a general chemical formula of (C.sub.6 H.sub.5 CO).sub.2 O.sub.2. Benzoyl peroxide is a non-toxic, colorless, odorless, and tasteless crystalline solid with a molecular weight of 242.22 and a melting point of between 103.degree. to 106.degree. C. It is known that benzoyl peroxide is sparingly soluble in H.sub.2 O or alcohol and is soluble in benzene, chloroform and ether. Other uses of benzoyl peroxide include use as an oxidizer in bleaching oils, flour, etc., as a catalyst in the plastics industry and as an initiator in polymerization. Commonly, benzoyl peroxide is available in a hydrous form (wet form) as a crystal. The water in the granules of hydrous benzoyl peroxide is utilized to reduce flammability and shock sensitivity.
Various commercially available products containing benzoyl peroxide for the treatment of skin conditions are available on the over the counter market from companies such as Norcliff Thayer of Tarrytown, N.Y., Westwood Pharmaceuticals of Buffalo, N.Y., and Richardson-Vicks of Wilton, Conn. In these commercially available, over-the-counter products utilized by consumers, the concentration of benzoyl peroxide is up to 10% benzoyl peroxide by weight. The 10% maximum is approved for over-the-counter preparations by the Federal Food and Drug Administration.
Prior to the present invention, the only way to deliver benzoyl peroxide for topical use has been in suspension form where finely ground particles of benzoyl peroxide are disbursed and suspended in various lotions, creams or gel bases. These preparations are available to the general public as an over-the-counter product or available in higher benzoyl peroxide strengths by prescription from a physician. Although benzoyl peroxide is soluble in some industrial solvents, such as aromatic solvents including toluene and methel-ethyl keytone, these industrial solvents are highly flamable and are irritant for human use. Therefore, the preparations are unusable in the over-the-counter drug market or the prescription markets. The exception is the use of acetone to place the benzoyl peroxide in solution.
Acetone is used to a limited degree in some topical formulations. The use of acetone is greatly limited by the fact that acetone is a primary irritant, extremely drying and presents a severe fire hazard, i.e., is flammable. Tests have shown that over-the-counter preparations use crystallized or insoluble benzoyl peroxide notwithstanding the presence of acetone. Therefore prior to this invention, existing benzoyl peroxide products utilized benzoyl peroxide in crystalline form and the crystals were suspended in a liquid or gel.
One known, prior art product by Richardson-Vicks, Inc., sold under the trade name Clearasil, includes benzoyl peroxide at 10% concentration as an active ingredient along with the following ingredients: water, aluminum hydroxide, isopropyl stearate, PEG-100 stearate, glyceryl stearate, cetyl alcohol, glycereth-26, isocetyl stearate, glycerin, dimethicone copolyol, sodium citrate, citric acid, methylparaben, propylparaben, and fragrance. An examination under a 40X power (objective power) microscope of this product revealed that the benzoyl peroxide is still in crystalline form and hence is not solubilized within the lotion.